US: Syria truce Russia's moment to 'put up or shut up'

Barely two hours before the Syria ceasefire was due to go into effect, the United States warned Russia that it was time to "put up or shut up."

State Department deputy spokesman Mark Toner said Washington had received assurances from Moscow that it would not bomb the "moderate opposition" after the truce.

"I don't know how to put it any better than saying: 'It's put up or shut up time,'" Toner told reporters.

"It is time for them to show through action rather than words that they are serious about what they profess to be serious about, which is a ceasefire, a cessation of hostilities and a political process that leads to a transition."

As he spoke, intense Russian bombing of rebel bastions was continuing in Syria in the runup to a ceasefire due to take effect at 2200 GMT.